Technique is very important and it is prudent to ALWAYS practice with multiple partners of all sizes.  This is an interesting question because in most videos, e.g. instructional, attackers are generally similar in size and especially with HKD, it appears that the attacker is not attacking at full speed or power and "acting" with aerial falls.

 

Having been in production of some 14 videos and 6 books, here's my take on it.  With video, there is a trade off on safety, "reality", & accurately depicting techniques.  It is primarily for instructional purpose and safety of the attacker a necessity, that video is shot with the attacker appearing to not go "full" speed.  With an escalation in force and speed of attack, the defense would also need to be escalated in speed and force.  It will likely not demonstrate technique well for instructional purposes, and, it is likely to cause injury (perhaps severe) to the attacker executing a technique at full speed and power (imagine a pressure point strike done full power and speed - likely not good for the attacker).  So there is a trade off of needing to provide a "realistic" attack and the need for safety and instruction.  

 

For the attacker, it is critical that they "go with the flow (the defense)" or they will end up with broken bones, dislocations, or other serious injury.  In reality, would someone do a pretty aerial fall in response to a technique?  Likely not, but they will likely go in the same general direction with injury in tow with further injury upon landing on their head, back, etc.  

 

Demonstrations are just that, they are by definition quite flashy and intended to draw audiences.  I've done demos where the applause died down on techniques which I knew were devastating but that didn't have a flashy fall or acrobatics.  There is a discipline that practices pressure point attacks but no falls.  Their philosophy, when done correctly and at full speed / power, the attacker is not going to be conscious and/or able to fall.  Hence, no falling practice.  Those demos to the untrained lay person, were quite unimpressive.  

 

A good friend of mine commented the same, "it looks like I'm falling way before you make contact with me".   He was correct, but I responded with "did you want to retry that in real time and see if I can pull back at the exact moment without causing injury?".  I suppose stunt people might have this down better but they get paid to take the injuries and their professional lives are not going to be long.  Certainly we need to train realistically but weigh the cost and benefit.  Given we most likely have lives outside the school, safety is something that can't be ignored.

 

Generally, correct technique will work in most situations.  There will always be exceptions, extreme physiques, drugs, that likely will require other techniques to release, set up, or enhance a given technique.  Knife edge kick to shin, hand strike or distraction, etc., might prove to be helpful to loosen a hold or to set up for the intended attack.  However, I can't stress the importance of perfection of technique because all the set up, distraction, etc. is not going to help if your technique is not any good.